A few observations on Hermann Grid stimuli

The Hermann Grid is made up of a series of vertical and horizontal bars. The Hermann Grid Illusion consists in the brightness of the intersections appearing different from that of the sections between intersections in spite of the luminance being the same. In the case of a light grid on a dark background the intersections tend to appear darker than the parts between intersections. It is here pointed out, in two different ways, that the stimulus power is less for the parts of the grid located at intersections than for parts of the grid between intersections. This is all in the stimuli and does not depend on vision or the visual system. Were we to assume that a stronger stimulus gives a brighter appearance this would make the parts between intersections appear brighter than the parts of the grid at intersections. This would be consistent with the Hermann Grid Illusion.